1. Field of the Invention
The present invention relates generally to a device for locating lost articles, and more particularly, to a portable locator device that communicates with a transceiver through radio frequency signals to determine the relative distance and/or direction of the transceiver from the locator unit.
2. Description of the Related Art
Many devices have been proposed for the location of various types of objects. Most of these devices are limited to tracking a certain type of object, such as a child or a set of keys, or are confined to only occasional uses. Many of these devices are also limited in their range of applications due to such limiting factors as operating range, battery life, or the inability to selectively locate large numbers of different articles.
For example, the inventions described by U.S. Pat. No. 5,289,163 issued Feb. 22, 1994 to Perez, U.S. Pat. No. 4,785,291 issued Nov. 15, 1988 to Hawthorne, U.S. Pat. No. 5,900,817 issued May 4, 1999 to Olmassakian, U.S. Pat. No. 5,652,569 issued Jul. 29, 1997 to Gerstenberger et al., U.S. Pat. No. 6,127,931 issued Oct. 3, 2000 to Mohr, or U.S. Pat. No. 4,785,291 issued Nov. 15, 1988 to Hawthorne, generally relate to a form of an electronic leash for child monitoring.
These devices require the caregiver to activate the caregiver""s monitoring device and child""s transceiver device, and attach the transceiver to the child so that the child may be located if the parent and child become separated. While such devices may be useful in some circumstances, such as a shopping trip or a visit to the park, it is well known that children may wander away from their caregivers at any time without warning. If the child""s transceiver device has not been activated before the child wanders away, the transceiver cannot be located by the caregiver""s device.
Additionally, these systems rely on relatively constant communications between the child""s transceiver device and the monitoring device. The need for constant communications between the transceiver and monitoring device disadvantageously requires the consumption of a large amount of power from the transceiver""s battery. As a result, the transceiver may not have usable battery power at critical times in which the parent desires to locate the child.
Another class of locator devices is described, for example, in U.S. Pat. No. 5,939,981 issued Aug. 17, 1999 to Renney, U.S. Pat. No. 5,294,915 issued Mar. 15, 1994 to Owen or U.S. Pat. No. 6,166,652 issued Dec. 26, 2000 to Benvenuti. In general, these locator devices include a radio transmitter that is used to activate a radio receiver attached to an article, such as a television remote control or set of keys. When the receiver is activated, it emits an audible signal that alerts the user to location of the article to which the receiver is attached. Unfortunately, these systems are only useful over a relatively small area due to the limited range of the audible signal.
Accordingly, there is still an unfulfilled need for an article locator system that is power efficient, able to selectively locate multiple articles, and able to accurately locate articles beyond the immediate area of the locator device.
The present invention solves these and other problems by providing an article locator system that includes a locator unit and one or more transceiver units. The transceiver, also referred to as a tag, is battery powered and relatively small in size so that it can be easily and non-obtrusively attached to an object that the user may need to locate at some time in the future. In one embodiment, a unique digital address code is stored in each transceiver.
The locator unit is capable of storing one or more digital address codes corresponding to the address codes stored in the receiver units. A user can search for a particular object by selecting the digital address code that corresponds to the code stored in the locator unit that is attached to the object the user desires to locate. The selected digital address code is then transmitted by wireless means from the locator unit to transceiver devices within range of the locator unit.
In one embodiment, in order to conserve power, the transceiver does not always remain activated. Instead, the transceiver periodically activates its receiver in order to determine if a signal is being sent from a locator device. When an address code is transmitted by the locator unit, all of the transceivers within range of the transmission will, at their next receiver activation cycle, detect the wireless transmission from the handheld locator. Each transceiver decodes the digital address signal and compares it to the unique address stored within the transceiver. If the address code transmitted by the locator device matches the address code stored in the transceiver, the transceiver activates its wireless transmitter and transmits a short-duration response signal. The locator device includes a wireless receiver that detects the wireless signal response from the selected transceiver. From this response signal, the distance and/or relative direction of the selected transceiver from the locator can be determined. This information is then displayed to the user.
The present invention is particularly advantageous, because in one embodiment, it provides the user with a variety of methods by which to locate an object to which a transceiver has been attached. This allows the user to best select the means that is most suited to the type of search the user is conducting. For instance, in various embodiments, the user may chose to locate a transceiver by measuring its bearing from the locator unit, its distance from the locator unit, or both its bearing and distance from the locator unit. Furthermore, in one embodiment, the user may chose to locate a transceiver by directing the transceiver to activate an indicator, such as an audible-tone or light, to alert the user as to the location of the transceiver.
The present invention is also particularly advantageous because, in various embodiments, it automatically selects the best search option for the user. For instance, in one embodiment, if the locator unit comes within a certain distance of the transceiver, the locator unit will instruct the transceiver to activate its indicator, such as a tone or light, to assist the user in locating the transceiver. In various embodiments, other functions can also be automated, thereby eliminating the need for the user to make decisions. For instance, in one embodiment, if the locator unit is experiencing interference in receiving a signal from a transceiver, the locator unit can request the user to move the locator unit to a different position. In a further embodiment, the locator system can automatically vary the signal strengths of the search and return signals, and can tune the receivers and transmitters of the locator unit and receiver to optimize performance. In these embodiments, the present invention presents the user with a wide range of search options, and can also select the options best suited to the environment in which the user is in. This eliminates the need for the user to make such decisions, thereby simplifying the search process for the user, while at the same time optimizing the search and locate performance.
In one embodiment, the article locator system includes a locator module and a transceiver. The locator module includes a first memory unit operable to store one or more first address codes, a user control operable to allow a user to select one of the stored first address codes, a first transmitter operable to wirelessly transmit a locator signal, wherein the locator signal includes one of the selected first address codes, a first receiver operable to receive a return signal transmitted by a transceiver module, and an antenna array operably connectable to the first transmitter and the first receiver. In one embodiment, first receiver is only active for a limited period after the locator signal is sent. The first control unit is operable to calculate a relative direction of the transceiver module from the locator module. The first control unit is linked to the first memory unit, the user control, the first transmitter, and the first receiver. The locator module can also further include a display screen linked to the first control unit.
In one embodiment, the locator module sends commands to said transceiver module. In one embodiment, the first transmitter transmits the first address code using frequency shift keying. In one embodiment, the locator signal includes a spread spectrum signal, an ultra wide band signal, a wideband FM signal, or a CDMA signal.
The transceiver includes a second memory unit operable to store a second address code. In one embodiment, the second memory unit is also operable to at least temporarily store a session identifier. The transceiver also includes a second receiver operable to receive the locator signal transmitted from the locator module, a second transmitter operable to wirelessly transmit the return signal, and a second control unit operable to compare the selected first address code transmitted by the locator module with the second address code. If the two codes are the same, the second control unit activates the second transmitter to wirelessly transmit the return signal. The second control unit is linked to the second memory unit, the second receiver, and the second transmitter. The transceiver also includes a timer linked to the second receiver and the second control unit. The timer is operable to activate the second receiver and second control unit at a specified time interval and for a specified time period. In one embodiment, the timer is a real time clock.
The transceiver can include an outer housing that can be waterproof. The transceiver module can also include a battery that is operable to power the second memory unit, the second receiver, the second transmitter, the second timer, and the second control unit. In one embodiment, the transceiver module is powered by radio frequency energy.
In one embodiment, the transceiver includes a sensor linked to the second control unit. In one embodiment, the sensor is operable to measure temperature. The transceiver can also further include an indicator linked to the second control unit.
In another embodiment, the locator module further includes a second timer linked to the first. The second timer is operable to determine the time between when the locator signal is transmitted to when the return signal is received. The first control unit operable to calculate a distance of the transceiver module from the locator module. In another embodiment, the locator unit includes a real-time clock. In one embodiment, the real time clock is programmable to activate the second receiver at specified times. In yet another embodiment, the real time clock is operable to be programmed by the locator module.
In one embodiment, the locator module is configured to allow the user to specify a known distance from the locator module to the transceiver module, use the known distance to determine an expected time period between when a locator signal is sent to the transceiver module to when the return signal should be received by the locator module, measure an actual time period from when the locator signal is sent to the transceiver module to when the return signal is received by the locator module, obtain an electronic system delay time by subtracting the actual time period from the expected time period, and store the electronic system delay time in the first memory unit.
In another embodiment, the locator unit includes a first sensor operable to measure a first temperature. The transceiver comprises a second sensor operable to measure a second temperature. The first and second temperatures can be used in calculating the system delay time.
In one embodiment, the locator unit calculates the distance of the transceiver module from the locator module by determining a total time elapsed from when the locator signal is sent to when the return signal is received by the locator device, subtracting an electronic system propagation delay time, and dividing by two. In another embodiment, the locator module determines distance to the transceiver module by switching between antennas in the antenna array according to a commutation frequency selected to minimize a tone output from said first receiver. In yet another embodiment, the locator module determines distance to the transceiver module by switching between antennas in the antenna array according to a commutation frequency selected to minimize a tone output from said first receiver. The commutation frequency can be swept across a desired range of frequencies.
In a further embodiment, the locator module is configured to measure a phase delay between a tone transmitted to the transceiver module and a tone received from the transceiver module. In one embodiment, the locator module is configured to calibrate to the transceiver module. Specifically, the locator module configured to measure a phase delay between a tone transmitted to the transceiver module and a tone received from the transceiver module when said transceiver module is relatively close to the locator module, convert the phase delay to a time delay, and store the transceiver delay time. In one embodiment, the first control unit of the locator unit is further operable to measure and store a signal processing time delay through the electronic system.
In one embodiment, the locator module further includes a switch to operably connect said first receiver to said antenna array. In one embodiment, the control unit controls a commutation rate of said switch.
In one embodiment, the locator module includes a conflict detection receiver that is linked to the first control unit and operable to detect a second locator signal transmitted from a second locator module. The first control unit can be further operable to delay the transmission of the locator signal from the first transmitter unit when the conflict detection receiver detects the second locator signal. In one embodiment, the conflict detection receiver can be integral with the first receiver.
The antenna array of the locator unit can include one or more antennas. The antennas can be pivotally coupled to the locator module. In one embodiment, the antenna array comprises two or more antennas coupled to the locator module and arranged in a circular path. In one embodiment, there are three or more antennas. In one embodiment, the first control unit is further operable to determine the strength of the return signal received at each of the antennas, and is operable to select the antenna receiving the strongest return signal. In one embodiment, the antennas are monopole-type antennas, dipole-type antennas, or patch-type antennas. In one embodiment, the locator module determines bearing to the transceiver module by switching between antennas in the antenna array and using Doppler processing to determine a direction of a wireless signal received from the transceiver module.
The locator unit can also include an internal compass unit operable to convert a relative direction of the transceiver module to a magnetic bearing. In one embodiment, the article locator system further includes a third transmitter operable to send a first signal to a second locator unit, and further including a third receiver operable to receive a second signal from a second locator unit. The article locator system can also include one or more additional locator units, wherein the locator unit and the additional locator units are connected by a communication path. This communication path can be a variety of pathways, including the internet.
The present invention is also directed to a method for locating an object. The method includes attaching a transceiver to the object. The transceiver includes a first receiver operable to receive a locator signal that contains a first address code, a first transmitter operable to wirelessly transmit a return signal, a first control unit operable to compare a second address code stored in a first memory unit with the address code contained in the locator signal. If the two codes are the same, the first control unit can wirelessly transmit the return signal. The first control unit is linked to the first memory unit, the first receiver, and the first transmitter. The transceiver also includes a first timer linked to the first receiver and the first control unit, the first timer operable to activate the first receiver and first control unit at a specified time interval and for a specified time period.
The method also includes entering and storing the first address code in a locator unit. The locator unit includes a second memory unit operable to store the first address code, a user control operable to allow a user to input the first address code and select the first address code after it has been entered and stored, a second transmitter operable to wirelessly transmit the locator signal, wherein the locator signal includes the selected first address code, a second receiver operable to receive the return signal transmitted by the transceiver module, one or more antennas linked to the first receiver, and a second control unit operable to calculate a relative direction of the transceiver module from the locator module. The second control unit is linked to the second memory unit, the user control, the second transmitter, and the second receiver.
The method further includes selecting the first address stored in the locator unit and activating the locator unit to wirelessly transmit the first address code to the transceiver. If the transceiver receives the locator signal containing the first address code and verifies that the first address code matches the second address code stored in the transceiver, the return signal is sent from the transceiver to the locator module, and the locator module analyzes the return signal to determine the relative direction of the transceiver.
The locator unit can further include a second timer linked to the second control unit that is operable to determine a time between when the locator signal is transmitted to when the return signal is received. The second control unit can be further operable to calculate a distance of the transceiver module from the locator module.
In one embodiment, the first timer activates the first receiver and the first control unit for a period of time at regular intervals. In another embodiment, the first timer is a real-time clock, and the user can program the real time clock to activate the first receiver and the first control unit at predetermined times.
In another embodiment, the present invention is directed to a system that includes a locator module and a transceiver. The locator module includes a first radio frequency transmitter operable to transmit a first address code, a first receiver configured to receive a return signal transmitted by a second transmitter, an antenna array operably connectable to the first transmitter and the first receiver by a switch, and a first control unit operable to control the switch. In one embodiment, the first address code is sent using frequency shift keying or phase shift keying. In one embodiment, the first control unit is operable to determine the bearing of a transceiver module from the control unit. In another embodiment, the first control unit is operable to determine the distance of a transceiver module from the control unit. In yet another embodiment, the first control unit is operable to determine both the bearing and the distance of the transceiver module from the control unit. In one embodiment, the first control unit controls a commutation rate of the switch. The locator module can also further include an internal compass unit operable to convert a relative direction of the transceiver module to a magnetic bearing. In one embodiment, the locator unit is operable to send commands to the transceiver.
The transceiver module includes a second receiver operable to receive the signal transmitted by the first transmitter, a second transmitter operable to transmit the return signal, and a second control unit operable to compare the first address code transmitted by the locator module with an address code stored in the transceiver module. If the two codes are the same, the second control unit activates the second transmitter to transmit the return signal. In one embodiment, the transceiver includes a timer operable to activate the second receiver and second control unit at a specified time interval and for a specified time period.
In one embodiment, the first control unit is further operable to calibrate and store a signal processing time delay through the transceiver module. In one embodiment, the distance from the locator module to the transceiver is calculated by determining a phase delay between a transmitted tone frequency modulated onto a first carrier and a received tone frequency modulated onto a second carrier.
In one embodiment, the locator module determines range to the transceiver module by commutating between antennas in the antenna array according to a commutation frequency selected to minimize a tone output from said first receiver. In another embodiment, the locator module determines range to the transceiver module by switching between antennas in the antenna array according to a commutation frequency selected to minimize a tone output from said first receiver. The commutation frequency is swept across a desired range of frequencies.
In yet another embodiment, the locator module is configured to measure a phase delay between a tone transmitted to the transceiver module and a tone received from the transceiver module. In one embodiment, the locator module is configured to calibrate to the transceiver module. Specifically, the locator is configured to measure a phase delay between a tone transmitted to the transceiver module and a tone received from the transceiver module when said transceiver module is relatively close to the locator module, convert the phase delay to a time delay, and store the system delay time.
In one embodiment, the locator module determines bearing to the transceiver module by commutating between antennas in the antenna array and using Doppler processing to determine a direction of a wireless signal received from the transceiver module.
In another embodiment, the present invention is directed to an apparatus that includes a locator module and a transceiver. The locator unit includes a means for transmitting a first address code using a first frequency band across a wireless channel, a means for receiving a return signal transmitted in a second frequency band in response to said first address code, an antenna array operably connectable to the means for transmitting and the means for receiving, and a means for determining a distance to a source of said return signal by commutating among antennas in said antenna array.
The transceiver includes a means for receiving a first frequency band signal containing a transmitted address code, a means for comparing the transmitted address code with a stored address code, a means for transmitting a second frequency band loop-back tone return signal for a specified period of time when said transmitted address code matches said stored address code, and a means for activating the means for receiving at desired intervals.
In another embodiment, the present invention is directed to a method for range determination. The method includes providing an unmodulated carrier signal at a first frequency to a switch, the switch configured to commutate among antennas in a antenna array at a commutation frequency to transmit a first modulated signal modulated according to the commutation frequency. The method also includes receiving the modulated signal in a tag receiver, an output of the tag receiver provided to a tag transmitter, transmitting a second modulated carrier from said tag transmitter, the second modulated carrier modulated according to said commutation frequency, receiving the second modulated carrier in a second receiver, adjusting said commutation frequency to minimize an output of the second receiver; and calculating a distance based on said commutation frequency.